Fuse plug



C. PECKERMAN FUSE PLUG Filed Aug. 6, 1931 ,7 as. .W

IIIIIIIIIIIIII wwf ATTORNEYS Patented Oct. 9, 1934 4FUSE PLUG CharlesPeckerman, New York, N. Y.

Application August 6, 1931, Serial No. 555,501

4 Claims.

My present invention in certain of its broad- -er aspects, is capable ofay wide and varied range of use in connection with fuse plugs ingeneral, but is especially adapted for em- 5 bodiment in a fuse plug ofthe type which employs a frangible transparent handle portion or top.

`The advantagesfof utilizing a glass topped fuse plug have long .beenrecognized. Such plugs permit ready inspection of the fusible ele-ments.When a number of plugs are arranged in a common fusebox ready detectionof a blown fuse is possibledue to the manner in which the glass becomesdiscolored from the products of combustion when a fusible element burnsout. Furthermore they appeal to the general public ybecause of the factthat many persons fearing electric shocks and overly cautious aboutreplacing fuses,` have 'much more coniidence in handling a glass memberthan rkthey rwould in handling the ordinary metallic topped plug ormetal rimmed plug.

VOne diniculty'which has heretofore. been encountered in connection withthe use of plugs of this character, has been the danger of the vglassshattering orcracking when the fusible elementburned. Such shatteringoccurred because of the sudden generation of an intense heat at theinteriorof the glass due to the metallic vapors and other 4products ofcombustion from the burning fuse, the cracking or shattering tendencybeing further increased by the sudden expansion of the air within theplug. Such shattering was not only productive of undesirable re hazards,but rendered a broken plug diiiicult to remove without danger ofinjuring the iingers, unless special tools were used to extract thebroken plug from its socket.

An object of the present invention is toretain all of the advantages ofusing the glass `topped plugs and yet eliminate the danger of shatteringthe frangible materialwhen a fuse blows. f

Another object is to provide a plug of extremely simple, practical,rugged, durable, inexpensive construction, well suited to meet therequirements of convenient manufacture and facile removal andreplacement.

Another object is to accomplishr the foregoing desiderata with butslight change in the .construction of a substantially conventional:-ized type of plug,y the only new element required in accordance with oneembodiment of the invention being a small heat absorbing disc of fibrousmaterial, such as cardboard,v asbestos or the like, introduced into theinterior of the plug asan incident of its manufacture.

In accordance with a preferred embodiment of the invention, the fusibleelement has one end anchored as usual to a terminal button securedwithin a socket member of porcelain or equivalent material. The otherend of the fuse extends through the hollow chamber defined by the socketpiece and the glass handle portion and is soldered or otherwise securedto the threaded terminal sleeve which encircles the assemblage andclamps the glass. handle to the socket. The above described standardconstruction is modified by my invention in order to minimize the amountof fusible material which burns when an over--load of current passestherethrough. A small plate of heat absorbent material such as cardboardor thev like extends VV`transversely of the hollow interior of the plugand the fuse is led through a notch in the edge of the plate, carriedacross the plate closely adjacent the exposed surface of the latter andthen out between the socket and the handle to the terminal sleeve. Thusthe only portion of the fuse which actually burns, is a short length ofwire lying substantially directly upon the cardboard and having aweakened portion therein where ythe break may occur.- Consequently theactual amount of fusible material which burns, is less than in priortypes of constructions.

The exposed surface of the cardboard itself may char or become blackenedby products of combustion when the fuse element burns, but that sectionof the fusible element which lies below the cardboard and within thesocket, will not burn and in consequence, heat generation will beminimized tosuch an extent that there is no danger of the glass piececracking.

In accordance with other embodiments of the invention, substantiallysimilar results may be obtained by the use of a transparent Ycardboarddisposed above the link or by placing the link between two transparentcardboards.v An essential distinction between this type of constructionand prior devices is the fact that the present invention reduces heatgeneration, and `permits the use of ordinary glass, thus avoiding thenecessity for attempting to shield the Vglass from the heat or the needfor using specially prepared expensive glass. Y K

The invention may be more fully understood from the followingdescription in connection with the accompanying drawing, wherein: Y

Fig. 1 isv a perspective View of a fuse plug'em bodying the invention,

nate the glass top or handle of the fuse plug. v

This member consists preferably of a manually graspable upper end 11 ofany suitable cross section and an integral sleeve portion 12. A socket13 of porcelain or other insulating material is provided with anexternal flange 14, adapted to be held in abutting relationship with theend of the sleeve 12 by the use of a threaded metallic terminal sleeve15, having a flange 16 at one end to engage under the flange 14 andhavingkthreaded engagement with the sleeve 12, whereby the ange 14 maybe drawn tightly against the end of the sleeve 12 when the sleeve 15 isscrewed home. Y

e One end of the fuse 1'? (typically a flat fuse wire with a weakenedportion 1711) is attached in conventional fashion as by soldering at 20to aoterminal button 18 spun into engagement with the bottom of thesocket 13 through an opening l9-therein,

As thus far described, the plug may be substantiallyv conventional, thepresent invention residing more particularly in the manner in which thefuse wire is arranged within the plug, so Athat only a-*small lengththereof burns when the fuseblows and the heat generation is minimized. i

Ihave illustrated a heat absorbent disc 21 of cardboard or the like,resting upon ,the -top of the socket 13, the socket tapering inwardly asat I22 ,above the flange 14 and aording a shoulder .23.upon which thecardboard disc rests. yThejfuse 1'7V is trained through a slot 21a atone edge of the disc, `carried across the` upper face of the disc inclose -contiguity thereto and then passed between the flange 14 and theend of the sleeve 12, being carried upwardly along the outside of thesleeve and having its end 24 lying within a flattened portion or recess25 in the sleeve l2. The end of the fuse wire Y projects slightly abovethe top of the metallic sleeve yl5 and the two may be joined together bysoldering as at 26. e f e The end 24 of therfuse soldered in the recess25 not only assures a good electrical contact between the fuse and themetallic sleeve, but also prevents rotation of the metallic sleeve withrespectv to the member 10.

It is not my intention in this application to claim the theory ofoperation of the apparatus above described. The construction, however,has |been thoroughly tested and it has been demonstrated that thefrangible top, even though made of -ordinary molded glass does notshatter or .crack when a fuse blows. Without limiting myself thereforeto any definite theory of operation, the` following tentativeexplanation of the advantageous results obtained, is offered:-

.The length of fuse wire actually exposed for burning is less than inthe ordinary fuse Vplug of this character. `The only portion whichactually. burns and generates vapor, is that Lrun of Vthe fuseA'directly overlying the cardboard.

Therefore, less heat is generated and the danger of cracking the glasslessened. Furthermore, the cardboard subdivides the otherwise capaciouschamber cooperatively defined by the members 10 and 13, into twochambers.

The upper of these two chambers may for the sake of convenience, betermed the combustion chamber, since it is here that the actual burningof the fusible element occurs. The lower chamber may, for the sake ofdescriptive convenience, be referred to as the cushioning charnber,since when combustion occurs in the upper chamber, and the air thereinis suddenly eX- panded, with an effect which is almost explosive, thecardboard disc will yield under the pressure suddenly generated andrender the upper chamber substantially expansible to take care of thesudden combustion which occurs therein; This cushioning effect of thelower chamber combined with the cardboard is, of course supplementary tothe heat absorbing action of the cardboard or the other fibrous discwhich may be utilized'.

A contributing factor is Ibelieved-to be the fact that the. restrictedvolume of the combustion chamber .together with the discwhichcuts it offfrom the cushioning chamber, both tend .to vminimize convection currentswhichV in the absence of the partition ,forming cardboard, would aid inheating the glass. 1 Y 1 During the burning-of the fuse, the arc sshorter, the period of combustion is consequently shorter, the burningis in some manner choked due to the fact that the burning portion of thefuse vlies directly against the heatV absorbing disc and the resultdesired is `effected without `in `any way .attempting to shield theLglass itself from the heat. .In otherwords, the desired effect `isobtained not by theuse'of a heat vinsulating medium but by the use of.means to controlandv minimize the heat -which is generated. 1 Y f 1 Byusing a transparent cardboard disc 20 arranged above the fuse instead ofbelow it as shown in Fig. 5,l heat generation takes place almostentirely within the: socket 13, which will not crack or break, evenunder extreme heat, yet the advantages of a-visible fuse are retained.Furthermore, even with this form of the inventionk the arc is againchoked and much of the heat absorbed by the cardboard.

By using transparent cardboard discs 31, 32 above and below thehorizontal run'of the fuse wire (Fig. 6), even more effective heatabsorption by the cardboard and choking of the4 arc is accomplished.

YIt will thus be seen that there is herein described Vapparatus in whichthe several features of this invention are embodied, and which apparatusin its action attains the various objects of the invention and iswellsuited to meet the requirements of practical use.

As many changes could be made in the above construction, and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended that allVmatter contained in the above description orY shown in the accompanyingdrawing shall be interpreted-asillustrative and ;not in a limitingsense. 1

Having thus described my invention,.what I claim as new and desire tosecure by Letters Patent is as follows: y 1. In a .fuse plug having afrangible top, a fuse lWire and. heat absorbing spark choking platesclosely adjacent to and upon opposite sides of that portion of the Wirewhere a break occurs upon overloading of the fuse.

2. In a fuse plug having a glass top, a fuse Wire and heat absorbingspark choking plates closely adjacent to and upon opposite sides of thatportion of the Wire Where a break occurs upon overloading oi the fuse,the upper of said elements being transparent whereby the condition ofthe fusible element may be observed through the glass top.

3. A glass topped fuse plug, having a fusible

